Paste coating method

ABSTRACT

A ceramic capacitor having a ceramic body and terminal electrodes, the ceramic body being substantially a rectangular parallelopiped in shape, the terminal electrodes being provided at the two ends of the ceramic body in the length direction, each terminal electrode being provided to cover one end face of the ceramic body in the length direction, part of the two surfaces in the width direction, and part of the two surfaces in the thickness direction, wherein, when the length of the ceramic body is L1 and the maximum lengths of the terminal electrodes at the two surfaces of the ceramic body in the width direction are L 3  and L 4, 0 ≦|(L 4 −L 3 |/L 1≦ 0.0227 is satisfied. One surface among the two surfaces of the ceramic body in the width direction is the paste introduction side in the roller coating, while the other surface is the paste escape side in the roller coating.

This is a Divisional of application Ser. No. 10/378,976 filed Mar. 5,2003 now U.S. Pat. No. 6,771,485. The entire disclosure of the priorapplication is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ceramic electronic device and to apaste coating method and paste coating apparatus used for production ofthat ceramic electronic device.

2. Description of the Related Art

In chip capacitors and other ceramic electronic devices, cap-shapedterminal electrodes are formed at the two end faces of the ceramic body.More particularly, each of these cap shaped terminal electrodes isformed to cover one end face of the ceramic body in the lengthdirection, parts of the two surfaces of the body in the width direction,and parts of the two surfaces in the thickness direction.

To form such terminal electrodes, the general practice has been to usethe method of dipping the ceramic body in a conductor paste or coatingby a roller to coat a conductive paste on the two ends of the ceramicbody and then dry the conductive paste by heat treatment to solidify it.

Terminal electrodes formed by conductive paste sometimes differ in thelengths of the parts formed on one surface in the width direction andthe lengths of the parts formed on the other surface in the widthdirection due to the conditions under which the conductive paste iscoated.

If soldering on such a ceramic electronic device, the contact areasbetween the terminal electrode and solder at the two surfaces in thewidth direction will end up differing. Therefore, the terminal electrodewill receive stress of different magnitudes from the solder and theinconvenience of the phenomenon of the ceramic body standing up on itsown (Manhattan phenomenon) etc. will arise.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a ceramic electronicdevice able to avoid the Manhattan phenomenon of the ceramic body in thesoldering process and a paste coating method and paste coating apparatusable to be used for production of such a ceramic electronic device.

To achieve the above object, according to a first object of the presentinvention, there is provided a ceramic electronic device having aceramic body and terminal electrodes, wherein the ceramic body issubstantially a rectangular parallelopiped in shape; the electrodeterminals are provided at the two end sides of the ceramic body in thelength direction, each of the terminal electrodes provided to cover oneend face in the length direction of the ceramic body, part of the twosurfaces in the width direction, and part of the two surfaces in thethickness direction; and, when the length of the ceramic body is L1 andthe maximum lengths of the terminal electrodes at the two surfaces ofthe ceramic body in the width direction are L3 and L4,0≦|L4−L3|/L1≦0.0227 (1/44) is satisfied.

Experiments of the present inventors revealed that if the ratio(|L4−L3|/L1) is set in a range from 0 to 0.0227, the rate of occurrenceof the Manhattan phenomenon in the soldering process is kept low. Overthe ratio |L4−L3|/L1=0.0227, the rate of occurrence of the Manhattanphenomenon tends to abruptly increase. Therefore, according to theceramic electronic device of the present invention, it is possible toeffectively suppress the Manhattan phenomenon and eliminate thephenomenon of the ceramic body standing up in the soldering process.

Preferably, the ceramic body has a plurality of internal electrodes, theplurality of internal electrodes being stacked inside the ceramic bodyin the thickness direction at intervals from each other and beingconnected to the terminal electrodes at one end surface each in thelength direction. The effect of the present invention is particularlygreat in the case of a ceramic electronic device having such a ceramicbody.

Preferably, each of the terminal electrodes is formed by coating aconductive paste on one end face of the ceramic body in the lengthdirection by roller coating and heat treating it.

In this case, preferably one surface among the two surfaces of theceramic body in the width direction is a paste introduction side in theroller coating, while the other surface is the paste escape side in theroller coating.

Preferably, the boundary shapes of the terminal electrodes formed atparts of the two surfaces of the ceramic body in the width direction aredifferent. More preferably, the boundary shapes of the terminalelectrodes formed at parts of the two surfaces of the ceramic body inthe width direction are different, with one being a projecting typeshape and the other being a recessed type shape. Alternatively, theboundary shapes of the terminal electrodes formed at parts of the twosurfaces of the ceramic body in the thickness direction are inclinedwith respect to the end faces of the ceramic body in the lengthdirection.

When forming a terminal electrode on one end face of the ceramic body inthe length direction by roller coating, the boundary shape with the bodyof the terminal electrode easily becomes this shape. In this case, byapplying the present invention, it is possible to effectively suppressthe Manhattan phenomenon.

The surface of the terminal electrode may be formed with a plating film.This plating film may be a single layer or multiple layers.

According to a second aspect of the present invention, there is provideda paste coating method for forming terminal electrodes comprising thesteps of rotating a roller coated with a conductive paste on its outercircumference and moving a ceramic body in substantially the samedirection as the direction of rotation of the roller and bringing oneend surface of the ceramic body into contact with the conductive pastepresent on the outer circumference of the roller to coat it with theconductive paste, wherein, when the speed of movement of the ceramicbody is Vc and the peripheral speed of the roller at the circumferencein contact with the one end surface of the ceramic body is Vp, the ratioVp/Vc satisfies 0.95≦Vp/Vc≦0.98.

In this case, the ceramic body preferably has a plurality of internalelectrodes, the plurality of internal electrodes being stacked insidethe ceramic body at intervals from each other and being exposed at oneend surface each of the ceramic body.

Experiments of the present inventors confirmed that by setting the ratioVp/Vc to a range of 0.95 to 0.98 and executing the paste coating method,it is possible to keep the ratio (|L4−L3|/L1) of the terminal electrodesformed in the range from 0 to 0.0227. If setting the ratio Vp/Vc largerthan 0.98, the ratio (|L4−L3|/L1) of the terminal electrodes exceeds0.0227. Further, even if setting the ratio Vp/Vc smaller than 0.95, theratio (|L4−L3|/L1) of the terminal electrodes exceeds 0.0227.

By using the paste coating method of the present invention, it ispossible to effectively produce the above-mentioned ceramic electronicdevice resistant to the Manhattan phenomenon.

According to a third aspect of the present invention, there is provideda paste coating apparatus including a paste coating roller for coating apaste for forming terminal electrodes and a ceramic body movementdevice, the roller being driven to rotate; the ceramic body movementdevice moving the ceramic body in substantially the same direction asthe direction of rotation of the roller and bringing one end surface ofthe ceramic body into contact with paste present on the outercircumference of the roller; and, when the speed of movement of theceramic body is Vc and the peripheral speed of the roller at thecircumference in contact with the one surface of the ceramic body is Vp,the ratio Vp/Vc satisfies 0.95≦Vp/Vc≦0.98.

This paste coating apparatus is used to coat a conductive paste on theouter circumference of the roller. It rotates the roller in this stateand moves the ceramic body in substantially the same direction as therotational direction of the roller. Further, it brings one end surfaceof the ceramic body into proximity with the outer circumference of theroller. Due to this, the conductive paste on the outer circumference ofthe roller is coated on that surface of the ceramic body. Therefore, theabove paste coating method is realized and the above-mentioned ceramicelectronic device according to the present invention is obtained.

Preferably, in the latter position of the direction of movement of theceramic body with respect to the paste coating roller, a scrape-offroller is placed rotating in substantially the opposite direction to thedirection of movement of the ceramic body for controlling the thicknessof the paste coated on the one surface of the ceramic body.

By providing this scrape-off roller, it is possible to form a terminalelectrode of a uniform predetermined thickness on one end surface of theceramic body.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, wherein:

FIG. 1 is a perspective view of a ceramic electronic device according toan embodiment of the present invention;

FIG. 2 is a cross-sectional view along the line II—II of FIG. 1;

FIG. 3 is a cross-sectional view of an electronic device with terminalelectrodes without the plating film shown in FIG. 2;

FIG. 4 is a front view of an electronic device with terminal electrodeswithout the plating film;

FIG. 5 is a back view of an electronic device with terminal electrodeswithout the plating film;

FIG. 6 is a plan view of an electronic device with terminal electrodeswithout the plating film;

FIG. 7 is a graph of the number of occurrences of the Manhattanphenomenon with respect to the ratio (|L4−L3|/L1);

FIG. 8 is a schematic view of the configuration of a paste coatingapparatus;

FIG. 9 is a partial enlarged cross-sectional view of the paste coatingapparatus shown in FIG. 8;

FIG. 10 is graph of lengths L3 and L4 of terminal electrodes withrespect to the ratio Vp/Vc;

FIG. 11 is a graph of the characteristic of the ratio (|L4−L3|/L1) withrespect to the ratio Vp/Vc;

FIG. 12 is graph of lengths L5 and L6 of terminal electrodes withrespect to the ratio Vp/Vc; and

FIG. 13 is a graph of the characteristic of the ratio (|L6−L5|/L1) withrespect to the ratio Vp/Vc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail below while referring to the attached figures.

Ceramic Electronic Device

As shown in FIG. 1 and FIG. 2, the ceramic electronic device accordingto an embodiment of the present invention has a ceramic body 1 andterminal electrodes 31 and 32. The “ceramic electronic device” includesa chip capacitor, chip inductor, chip varistor, or chip resistor orcombinations of the same. Note that in the figures, a chip capacitor isshown as one example of a ceramic electronic device.

The ceramic body 1 is substantially a rectangular parallelepiped inshape. Note that the expression “rectangular parallelepiped” includesrectangular parallelepiped with rounded corners and rectangularparallelepiped which are chamfered. The length L1 along the lengthdirection L of the ceramic body 1, the width W1 along the widthdirection W, and the thickness T1 along the thickness direction T may beany values. In the case of the illustrated embodiment, the values are asfollows: length L1=2.0 mm, width W1=1.2 mm, and thickness T1=1.25 mm. Asanother example, they may be a length L1=4.4 mm, a width W1=3.1 mm, anda thickness T1=2.2 mm.

The relative magnitude of the length L1, width W1, and thickness T1 islength L1>width W1 and length L1>thickness T1. The ceramic body 1 may beformed from a known ceramic material selected in accordance with thetype of the ceramic electronic device. Note that the length direction Lis the direction in which the terminal electrodes are formed at the twoends of the ceramic body 1, while the thickness direction T is thedirection in which the internal electrodes 21 to 28 shown in FIG. 2 andthe dielectric layers formed between them are stacked. Further, thewidth direction W is the direction substantially perpendicular to boththe length direction L and thickness direction T.

Referring to FIG. 2, the ceramic body 1 has a plurality of internalelectrodes 21 to 28. The plurality of internal electrodes 21 to 28 arestacked inside the body in the thickness direction T via dielectriclayers. In the present embodiment, the alternate internal electrodes 21,23, 25, and 27 stacked via dielectric layers are connected to only oneterminal electrode 31, while the other internal electrodes 22, 24, 26,and 28 are connected to only the other terminal electrode 32, so as toform a multilayer capacitor circuit. Note that the number of theinternal electrodes 21 to 28 is not particularly limited in the presentinvention.

Referring to FIG. 3, the terminal electrodes 31 and 32 are provided atthe two sides of the ceramic body 1 in the length direction L. Furtherreferring to FIG. 4 to FIG. 6 as well, one terminal electrode 31 isprovided so as to cover one end surface 11 of the body 1 in the lengthdirection L, parts of the two surfaces 13 and 14 in the width directionW, and parts of the two surfaces 15 and 16 in the thickness direction T.The other terminal electrode 32 is provided so as to cover the other endsurface 12 in the length direction L, parts of the two surfaces 13 and14 in the width direction W, and parts of the two surfaces 15 and 16 inthe thickness direction T.

Referring to FIG. 4, one terminal electrode 31 covers the part of thesurface 13 in the width direction W near one end surface 11 in thelength direction L. The other terminal electrode 32 covers the part ofthe surface 13 in the width direction W near the other end surface 12 inthe length direction L. Note that the terminal electrodes 31 and 32 aredifficult to form at uniform widths (length direction L of body 1) atthe two ends of the ceramic body 1 in the length direction L. Theysometimes become recessed as the center as shown in FIG. 4, project outat the center as shown in FIG. 5, or become asymmetric at the two sidesas shown in FIG. 6. The paste coating method by the paste coatingapparatus explained later has a large influence over such shapes.

In FIG. 4, the maximum length of the terminal electrodes 31 and 32 atthe surface 13 in the width direction W is made L3. In FIG. 4, however,the boundary shapes of the terminal electrodes 31 and 32 are recessedshapes with recessed centers. The two side parts generally have maximumlengths of L3, but the parts of the maximum length L3 are not alwaysthere. The maximum lengths L3 of the terminal electrodes 31 and 32should be the same when forming them under the same conditions by thelater explained paste coating apparatus.

Referring to FIG. 5, one terminal electrode 31 covers the part of theother surface 14 in the width direction near one end surface 11 in thelength direction L. The other terminal electrode 32 covers the part ofthe other surface 14 in the width direction W near the other end surface12 in the length direction. The maximum length of the terminalelectrodes 31 and 32 at the other surface 14 in the width direction W ismade L4. Note that in FIG. 5, the terminal electrodes 31 and 32 haveprojecting boundary shapes with projecting centers. The center partsgenerally have the maximum lengths of L4, but the parts of the maximumlength L4 are not always the centers. The maximum lengths L4 of theterminal electrodes 31 and 32 should be the same when forming them underthe same conditions by the later explained paste coating apparatus.

Referring to FIG. 6, one terminal electrode 31 covers the part of thesurface 15 in the thickness direction T near the end surface 11 in thelength direction L. The other terminal electrode 32 covers the part ofthe surface 15 in the thickness direction T near the other end surface12 in the length direction L. When viewed from the thickness direction Tsurface 15 side, the boundary shapes of the terminal electrodes 31 and32 with the body are inclined with respect to the end faces 11 and 12.Further, the lengths of the terminal electrodes 31 and 32 on the surface13 in the width direction W are made L5, while the lengths of theterminal electrodes 31 and 32 on the other surface 14 in the widthdirection W are made L6. In the present embodiment, the length L5positioned at the surface 13 in the width direction W serving as thepaste introduction side in the later explained roller coating is smallerthan the length L6 positioned at the surface 14 in the width direction Wserving as the paste escape side.

This length L5 often matches with the maximum length L3 shown in FIG. 4,but the length L6 is often shorter than the maximum length L4 shown inFIG. 5. Note that at the other surface 16 in the thickness direction Tas well, the boundary shapes of the terminal electrodes 31 and 32 aresimilar to the boundary shapes of the terminal electrodes 31 and 32 atthe surface 15.

Referring to FIG. 3, one terminal electrode 31 is connected to theinternal electrodes 21, 23, 25, and 27 at one surface 11 of the ceramicbody 1 in the length direction L. The other terminal electrode 32 isconnected to the internal electrodes 22, 24, 26, and 28 at the othersurface 12 of the ceramic body 1 in the length direction L.

The terminal electrodes 31 and 32 are electrodes baked on the ceramicbody 1. These terminal electrodes 31 and 32 are obtained by coating aconductive paste on the ceramic body 1 and drying and solidifying theconductive paste by heat treatment.

Referring again to FIG. 1 and FIG. 2, the surfaces of the terminalelectrodes 31 and 32 have plating films 41 and 42 deposited on them.Further, the surfaces of these plating films 41 and 42 have platingfilms 43 and 44 deposited on them. These plating films 41 to 44 aremetal films of Cu, Ni, Sn, etc.

The lengths L3 and L4 of the terminal electrode 31 (see FIG. 4 and FIG.5) are far larger than the thicknesses of the plating films 41 and 43deposited on the surface of the terminal electrode 31. The thicknessesof the plating films 41 and 43 are substantially negligible. Similarly,the lengths L3 and L4 of the terminal electrode 32 are far larger thanthe thicknesses of the plating films 42 and 44 deposited on the surfaceof the terminal electrode 32 and the thicknesses of the plating films 42and 44 are substantially negligible.

The important characteristic of the ceramic electronic device accordingto the present invention is that the length L1 of the ceramic body 1,the length L3 of the terminal electrodes 31 and 32 at the widthdirection W surface 13 side and the length L4 of the terminal electrodes31 and 32 at the other width direction W surface 14 side satisfy0≦|L4−L3|/L1≦0.0227(1/44)  (1)For example, if the length L1 of the ceramic body 1 is 2.0 mm, the aboverelation (1) becomes 0≦|L4−L3|≦0.046(1/22) mm

<Experimental Data>

Next, experimental data will be explained. Five sample groups 1 to 5 ofceramic electronic devices of the above configuration changedprogressively in the ratio (|L4−L3|/L1) of the terminal electrodes 31and 32 were prepared. The sample groups 1 to 5 each included 100samples. The ratios (|L4−L3|/L1) of the sample groups 1 to 5 were made0.002(1/500), 0.011(1/91), 0.021(1/48), 0.031(1/32), and 0.041(1/24).These values, however, were mean values of the 100 samples included inthe respective sample groups.

Next, soldering processes were applied to these sample groups 1 to 5 toinvestigate the occurrence of the Manhattan phenomenon. In the solderingprocesses, eutectic solder was used and the reflow temperature was made240° C. The results are shown in the following Table 1.

TABLE 1 No. of occurrences Ratio (|L4-L3|/L1) of Manhattan Sample groupno. (mean value) phenomenon 1 0.002 0 2 0.011 1 3 0.021 0 4 0.031 5 50.041 4

Next, the number of occurrences of the Manhattan phenomenon with respectto the ratio (|L4−L3|/L1) was graphed and approximated. The curve isshown by reference U8 in FIG. 7. Referring to this curve U8, in therange of the ratio (|L4−L3|/L1) from 0 to 0.0227, the number ofoccurrences of the Manhattan phenomenon in the soldering process is keptlow. Over a ratio |L4−L3|/L1=0.0227, the number of occurrences of theManhattan phenomenon abruptly increases.

Above, the case of application of the present invention to a chipcapacitor as one type of ceramic electronic device was explained, butthe present invention can also be applied to other types of ceramicelectronic devices.

Paste Coating Method and Paste Coating Apparatus

Next, the paste coating method and paste coating apparatus used forproduction of the above ceramic electronic device will be explained.

As shown in FIG. 8, the paste coating apparatus according to oneembodiment of the present invention includes a paste coating roller 61and a ceramic body movement device 8.

The roller 61 is driven to rotate in the direction indicated by thearrow a1 by a drive device 71. The outer circumference of the roller 61is coated with a conductive paste 35. Specifically, the bottom of theroller 61 is immersed in the conductive paste 35 placed in a container37. By driving the roller 61 to rotate, the outer circumference of theroller 61 is coated with the conductive paste 35. The conductive paste35 is formed from a material having a known composition, viscosity, andelectrical characteristics.

The roller 61 has a stationary squeegee 67 provided near it. Thestationary squeegee 67 scrapes off the excess conductive paste 35 coatedon the outer circumference of the roller 61 to ensure a uniformthickness of the conductive paste 35 coated on the outer circumferenceof the roller 61.

As shown in FIG. 8 and FIG. 9, the ceramic body movement apparatus 8moves the ceramic body 1 in the tangential direction a3 of therotational direction a1 of the roller 61 to bring one surface 11 of theceramic body 1 in the length direction L into proximity with the outercircumference of the roller 61. The ceramic body 1 is the same as theceramic body 1 explained with reference to FIG. 1 and FIG. 2 and is inthe state before formation of the terminal electrodes 31 and 32.

The movement direction a3 of the ceramic body 1 becomes substantiallyperpendicular to the shaft 611 of the roller 61. The ceramic bodymovement device 8 specifically has a belt 83 and guide roller 85 and 86.

The belt 83 is provided with a plurality of fasteners 81. Thesefasteners 81 are provided at intervals on the belt 83. ceramic bodies 1are affixed to the belt 83 through these fasteners 81.

The belt 83 is stretched between the guide rollers 85 and 86. The guideroller 86 is driven to rotate in the direction indicated by the arrow a4by a drive device 73. Due to this, the belt 83 travels in the directionof the arrow a3. The ceramic bodies 1 fastened to the belt 83 also aremoved in the direction of the arrow a3.

Referring to FIG. 8, the paste coating apparatus is provided with ascraper roller 62. This scraper roller 62 is provided after the roller61 in the direction of the arrow a3 and is driven to rotate in thedirection a2 opposite to the movement direction a3 of the ceramic body 1by a drive device 72. That is, the rotational direction a2 is reverse tothe rotational direction a3. The scraper roller 62 is provided with astationary squeegee 68. The stationary squeegee 68 serves to remove dirtfrom the outer circumference of the scrape-off roller 62.

The ceramic body movement device 8 brings the surface 11 of the ceramicbody 1 into proximity with the roller 61 as explained above, then movesthe ceramic body 1 in the direction a3 opposite to the rotationaldirection a2 of the scraper roller 62 and moves the surface 11 of theceramic body 1 into proximity with the outer circumference of thescraper roller 62.

The paste coating apparatus is provided with a control device 75. Thecontrol device 75 gives a control signal S1 to the drive device 71 tocontrol the rotation of the roller 61 through the drive device 71.Similarly, the control device 75 gives a control signal S2 to the drivedevice to control the rotation of the roller 62 through the drive device72. Further, the control device 75 gives a control signal S3 to thedrive device 73 to control the travel of the belt 83 through the drivedevice 73 and the guide roller 86.

Referring to FIG. 8 and FIG. 9, the apparatus rotates the roller 61coated on its outer circumference with a conductive paste 35, moves theceramic body 1 in the tangential direction a3 of the same direction asthe rotational direction a1 of the roller 61, and brings the surface 11of the ceramic body 1 in the length direction L into proximity with theouter circumference of the roller 61. Due to this, the conductive paste35 on the outer circumference of the roller 61 is coated on and near thesurface 11 of the ceramic body 1 in the length direction L. The onesurface 13 among the two surfaces 13 and 14 of the ceramic body 1 in thewidth direction W becomes the paste introduction side, while the othersurface 14 becomes the paste escape side (see FIG. 9).

As shown in FIG. 9, when the speed of movement of the ceramic body 1 ismade Vc and the peripheral speed of the roller 61 as seen at thecircumference Crl in contact with the surface 11 of the ceramic roller 1is made Vp, to obtain the ceramic electronic device shown in FIG. 1 toFIG. 6, it is sufficient to set the ratio Vp/Vc of the roller 61 andceramic body movement device 8 to satisfy:0.95 ≦Vp/Vc≦0.98  (2)In the illustrated embodiment, the ratio Vp/Vc can be controlled by thecontrol device 75.

Note that the circumference Crl shown in FIG. 9 is at a position of adistance L7 from the outer circumference of the roller 61 of preferably0 to 0.8 mm. Further, the thickness L8 of the conductive paste 35 formedon the outer circumference of the roller 61 is a thickness of 3 to 12times the distance L7.

Next, as explained with reference to FIG. 8, the apparatus rotates thescraper roller 62 in the direction indicated by the arrow a2, moves theceramic body 1 in a direction a3 opposite to the rotational direction a2of the scraper roller 62, and brings the surface 11 of the ceramic body1 into proximity with the outer circumference of the scraper roller 62.Therefore, the excess portion of the conductive paste 35 formed on thesurface 11 of the ceramic body 1 is scraped off from the outercircumference of the scraper roller 62.

Next, the conductive paste 35 coated on the surface 11 of the ceramicbody 1 is dried and solidified by heat treatment. By applying a similarpaste coating process and heat treatment to the opposite surface 12 ofthe ceramic body 1, the terminal electrodes 31 and 32 shown in FIG. 1 toFIG. 6 are obtained.

<Experimental Data>

Next, experimental data will be explained. In the above paste coatingmethod, the speed of movement Vc of the ceramic body 1 was fixed and theperipheral speed Vp of the roller 61 as seen at the circumference Crlcontacting the surface 11 of the ceramic body 1 was progressivelychanged (see following Table 2). Due to this, the ratio Vp/Vc wasprogressively changed. The result are shown as Numerical Value Examples1 to 6.

TABLE 2 Speed of Peripheral Peripheral movement speed of speed Vp ofNumerical Vc of outer roller 61 value ceramic circumference seen atexample body 1 of roller 61 circumference Ratio no. (mm/s) (mm/s) Cr1(mm/s) Vp/Vc 1 6.000 5.700 5.719 0.953 2 6.000 5.800 5.819 0.970 3 6.0005.900 5.920 0.987 4 6.000 6.000 6.020 1.003 5 6.000 6.100 6.120 1.020 66.000 6.200 6.221 1.037

The peripheral speed Vp of the roller 61 as seen at the circumferenceCr1 in contact with the surface 11 of the ceramic body 1 is found fromthe peripheral speed of the outer circumference of the roller 61. Thedistance L7 between the outer circumference of the roller 61 and thesurface 11 of the ceramic body (see FIG. 9) was made 0.1 mm. Further,the thickness L8 of the conductive paste 35 coated on the outercircumference of the roller 61 was made 1.1 mm.

Using the paste coating method of each of Numerical Value Examples 1 to6, conductive paste 35 was coated on and near the surface 11 of theceramic body 1 in the length direction L. The length L1, width W1, andthickness T1 of the ceramic body 1 were made 2.0 mm, 1.2 mm, and 1.25mm, respectively. Further, the composition and the viscosity of theconductive paste 35 were as follows:

-   -   <Paste Composition>

Metal ingredient: Ag 100%

Metal content: 73 wt %

Binder: acrylic-based resin

<Paste Viscosity>

1 rpm: 80 Pa·s

10 rpm: 35 Pa·s

100 rpm: 23 Pa·s

Here, the paste viscosity is the value measured by a BF viscosity meter.

Next, the coated conductive paste 35 was dried and solidified by heattreatment. Due to this, a sample provided with a terminal electrode 31on the surface 11 of the ceramic body 1 was obtained. Five types ofsamples were obtained for each of the Numerical Value Examples 1 to 6.

Next, the length L3 of the terminal electrode 31 at the width directionW surface 13 side and the length L4 of the terminal electrode 31 at thewidth direction W surface 14 side were measured (see FIG. 4 and FIG. 5).Further, the length L5 of the terminal electrode 31 on the surface 13 inthe width direction W and the length L6 of the terminal electrode 31 onthe other surface 14 in the width direction W when seen from thethickness direction T surface 15 side were measured. The surface 13 isthe paste introduction surface, while the surface 14 is the paste escapesurface (see FIG. 9). The lengths L3 to L6 were measured by a projector.

FIG. 10 is a graph of the lengths L3 and L4 of the terminal electrode 31with respect to the ratio Vp/Vc. In the figure, the characteristic ofthe length L3 with respect to the ratio Vp/Vc and the characteristic ofthe length L4 with respect to the ratio Vp/Vc are shown by references U3and U4, respectively. Referring to the characteristics U3 and U4, thelarger the ratio Vp/Vc, the shorter the length L3 of the terminalelectrode 31 on the paste introduction side surface 13 and the longerthe length L4 of the terminal electrode 31 on the paste escape sidesurface 14.

FIG. 11 is a graph of the characteristic U1 of the ratio (|L4−L3|/L1)with respect to the ratio Vp/Vc. This characteristic U1 is found fromthe characteristics U3 and U4 shown in FIG. 10. In the range of theVp/Vc of 0.96 or less, the smaller the ratio Vp/Vc, the greater theratio (|L4−L3|/L1). When the ratio Vp/Vc becomes smaller than 0.95, theratio (|L4−L3|/L1) exceeds 0.0227. Therefore, the lower limit of theratio Vp/Vc was made 0.95.

Further, in the range of the Vp/Vc of 0.97 or more, the larger the ratioVp/Vc, the greater the ratio (|L4−L3|/L1) When the ratio Vp/Vc becomesgreater than 0.98, the ratio (|L4−L3|/L1) exceeds 0.0227. Therefore, theupper limit of the ratio Vp/Vc was made 0.98.

If the ratio Vp/Vc is set in a range B1 of 0.95≦Vp/Vp≦0.98 in this way,it is possible to keep the ratio (|L4−L3|/L1) of the terminal electrode31 within the range of 0≦(|L4−L3|/L1)≦0.0227.

FIG. 12 is a graph of the lengths L5 and L6 of the terminal electrode 31with respect to the ratio Vp/Vc. In the figure, the characteristic ofthe length L5 with respect to the ratio Vp/Vc and the characteristic ofthe length L6 with respect to the ratio Vp/Vc are shown by references U5and U6, respectively.

Referring to the characteristics U5 and U6 shown in FIG. 12, the largerthe ratio Vp/Vc, the shorter the length L5 of the terminal electrode 31on the paste introduction side surface 13 when seen from the thicknessdirection T surface 15 side and the longer the length L6 of the terminalelectrode 31 on the paste escape side surface 14.

FIG. 13 is a graph of the characteristic U2 of the ratio (|L6−L5|/L1)with respect to the ratio Vp/Vc. This characteristic U2 is found fromthe characteristics U5 and U6 shown in FIG. 12. If the ratio Vp/Vc isset in a range B1 of 0.95≦Vp/Vp≦0.98, it is possible to keep the ratio(|L6−L5|/L1) of the terminal electrode 31 within the range B3 of0≦(|L6−L5|/L1)<0.0227.

As explained above, according to the present invention, it is possibleto provide a ceramic electronic device able to avoid the Manhattanphenomenon of the ceramic body in the soldering process and a pastecoating method and paste coating apparatus able to be used forproduction of such a ceramic electronic device.

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A paste coating method for forming terminal electrodes comprising thesteps of: rotating a roller coated with a conductive paste on its outercircumference and moving a ceramic body in substantially the samedirection as the direction of rotation of said roller; and bringing oneend surface of said ceramic body into contact with said conductive pastepresent on the outer circumference of said roller to coat the endsurface with said conductive paste, wherein, when the speed of movementof said ceramic body is Vc and the peripheral speed of said roller atthe circumference in contact with said one surface of said ceramic bodyis Vp, the ratio Vp/Vc satisfies 0.95 ≦Vp/Vc≦0.98, said ceramic body hasa plurality of internal electrodes, and said plurality of internalelectrodes being stacked inside said ceramic body at intervals from eachother and being exposed at said one surface each of said ceramic body.